A combined rolling membrane-balloon catheter is known from U.S. Pat. No. 5,662,703 A which is designed for deploying a self-expanding stent in the region of a stenosis in a bodily vessel. This catheter has an inner and an outer shaft, between the distal ends of which a rolling membrane which is doubled over on itself is provided, and which forms the distal end of the catheter. This rolling membrane forms a space, extending coaxially with the catheter, in front of the distal end of the inner shaft in which the self-expanding stent is accommodated in its contracted state.
A balloon which is expandable when acted on by pressure is proximally situated in front of the distal end of the inner shaft, and is used to assist in the expansion motion of the stent.
To be released, the outer shaft is moved relative to the inner shaft in the proximal direction, as a result of which the membrane which is doubled over on itself is retracted from the stent in a peeling motion to the rear, and gradually releases the stent. The stent gradually widens due to its self-expansion action until it is released as a result of the complete peeling of the rolling membrane to the rear. At the same time, the rolling membrane is pulled over the balloon in the proximal direction, the balloon then being, situated directly in front of the distal end of the catheter. The catheter may then be inserted into the expanded stent in the axial direction, and the balloon may be expanded by the action of pressure. The stent is thus optimally expanded, and stenoses present in the bodily vessel are also mechanically expanded. Since the balloon is present inside the rolling membrane, the entire system is particularly pressure-tight. If the balloon bursts, the rolling membrane situated around the balloon prevents the highly pressurized fluid from escaping into the bodily vessel. Instead, the pressure is relieved via the interior of the outer catheter.
A device for removing vein sections is known from U.S. Pat. No. 5,593,418 A, in which a rolling membrane is provided which may be unrolled over the vein to be removed, using a pressurized fluid. This device also has an anchoring balloon which is inflated inside the vein before the rolling membrane is unrolled in order to fix the vein with respect to the rolling membrane.
As background for the invention, it is further noted that basic requirements are imposed on the catheter used in the treatment of stenoses in bodily vessels. Thus, penetration into even narrow lesions with major damage should be possible with minimum friction, and at the same time, for achieving high expansion forces it should be possible for the balloons used to be acted on with high pressure. The balloons must have a correspondingly high pressure resistance, so that they are generally more rigid with regard to their material characteristics. In turn, this causes problems for penetration into narrow, damaged bodily vessels.
In the present interplay of various conflicting problems, rolling membrane catheters are basically known which, although they are able to penetrate into a stenosis or severely damaged vessel regions with very little friction, due to the necessity of rolling them over, such rolling membranes are very difficult to connect to a balloon lumen in a pressure-tight manner.
In addition, hydrophilic coatings of conventional balloon catheters are known for which, although the coefficient of friction for the balloon catheter may be greatly reduced, such a catheter may still become stuck in long, severely damaged lesions. Thus, as a rule a compromise must be found between flexibility and pushability of the catheter, which possibly may not be optimal for all clinical cases.
Lastly, another fundamental problem with such balloon catheters is that they are generally not anchored at their treatment site, i.e., in the region of a stenosis, for example.